1. Paper for the Journal Series, New Jersey Agricultural Experiment Station, New Brunswick, New Jersey. This reserach was supported by U.S.P.H.S. Research Grant #ES-00016 from Bureau of State Services.
2. Our gratitude to Shell Development Corp. for their generous gift of compounds I, II, IV, and V.
3. L. C. MITCHELL, JAOAC,44, 643 (1961).
4. J. ROBURN, Chem. Ind.,38, 1555 (1963).
5. We are grateful to W. B. DEICHMANN, University of Miami, for the natural exposure of dieldrin.